The implications of revised Quaternary palaeoshoreline chronologies for the rates of active extension and uplift in the upper plate of subduction zones
The implications of revised Quaternary palaeoshoreline chronologies for the rates of active extension and uplift in the upper plate of subduction zones
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修正的第四纪古海岸线年表对俯冲带上部板块主动伸展和隆起速率的影响
DOI：
10.1016/j.quascirev.2013.08.006
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发表时间：
2013
影响因子：
4
通讯作者：
Roberts G
中科院分区：
文献类型：
--
作者：
Roberts G
我们展示了一种确定第四纪古海岸线年代学的同步相关技术，以检验构造、气候和海平面变化之间的拟议关系。根据TIN DEM 1000万米数据和野外工作，测量了活动Vibo正断层周围卡拉布里亚海相古海岸线的高程，并与全球海平面曲线进行了对比。使用同步相关方法和新的U/Th数据来确定断层上的滑动速率与整个区域的隆升速率之间的关系。区域抬升可能与沿卡拉布里亚海沟俯冲有关，或由于密集的活动正断层的累积效应，其速度足够快，甚至足以抬升Vibo正断层的上盘；只有减去Vibo断层的滑动速率，才能确定背景抬升速率的实际值。29条高程剖面上的多条古海岸线与全球海平面的同步对比表明，所产生的抬升速率(背景抬升减去局部悬壁下沉)在0~340 Ka的时间内是恒定的，而不是以前提出的4倍的波动。抬升速率由断层中央的0.4亿mm/年增加到断层尖端附近的上盘的1.75亿mm/年。古海岸线可以从上盘追踪到断层尖端周围的下盘，因此可以在整个断层上进行对比。断层上的抛掷速率平均在340千卡以上，从断层中心的最大值(1毫米/年)下降到尖端的零。这种抛掷速率的梯度解释了沿断层产生的隆升速率的空间差异。我们将断头处及其以上的1.75亿mm/年的综合隆升速率解释为区域隆升的标志，推测与俯冲有关，但我们不能排除其他局部断裂影响这种隆升的可能性；断层上盘较低的隆升速率是由于与局部活动正断层相关的“区域”隆升和沉降之间的相互作用。我们讨论了(A)我们的同步相关技术应该如何引发对全球古海岸线年代学的重新评估，以及(B)对卡拉布里亚的构造和地震危险性的影响，表明隆起率场的扰动是绘制活动断层的位置、其变形速率以及俯冲带上方地震危险性的关键标准。
We demonstrate a synchronous correlation technique to determine the chronology of Quaternary palaeoshorelines to test proposed relationships between tectonics, climate and sea-level change. The elevations of marine palaeoshorelines in Calabria around the active Vibo normal fault have been measured from TIN DEM 10 m data and fieldwork and correlated with global sea-level curves. A synchronous correlation method and new U/Th dates are used to ascertain how the slip-rate on the fault relates to uplift rates across the region. Regional uplift, possibly associated with subduction along the Calabrian trench or due to the cumulative effect of closely-spaced active normal faults, is rapid enough to uplift even the hangingwall of the Vibo normal fault; the actual value for the rate of background uplift can only be ascertained once the rate of slip on the Vibo fault is subtracted. Synchronous correlation of multiple palaeoshorelines sampled along 29 elevation profiles with global sea-levels shows that the resultant uplift rate (background uplift minus local hangingwall subsidence) is constant through time from 0 to 340 ka, and not fluctuating by a factor of 4 as previously suggested. The uplift rate increases from 0.4 mm/yr at the centre of the hangingwall of the fault to 1.75 mm/yr in the hangingwall in the vicinity of the fault tip. Palaeoshorelines can be traced from the hangingwall to the footwall around the fault tip and hence correlated across the fault. The throw-rate on the fault averaged over 340 ka decreases from a maximum at the centre of the fault (1 mm/yr) to zero at the tip. This gradient in throw-rate explains the spatial variation in resultant uplift rates along the fault. We interpret the 1.75 mm/yr resultant uplift rate at and beyond the fault tip as the signature of a regional uplift, presumably related to subduction, although we cannot exclude the possibility that other local faults influence this uplift; the lower uplift rates in the hangingwall of the fault are due to interaction between “regional” uplift and subsidence associated with the local active normal faulting. We discuss (a) how our synchronous correlation technique should trigger a re-appraisal of palaeoshoreline chronologies worldwide, and (b) the implications for the tectonics and seismic hazard of Calabria, suggesting that perturbations in the uplift-rate field are a key criterion to map the locations of active faults, their deformation rates, and hence seismic hazard above subduction zones.
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